A {@code HashService} hashes input sources utilizing a particular hashing strategy. <p/> A {@code HashService} sits at a higher architectural level than Shiro's simple {@link Hash} classes: it allows for salting and iteration-related strategies to be configured and internalized in a single component that can be re-used in multiple places in the application. <p/> For example, for the most secure hashes, it is highly recommended to use a randomly generated salt, potentially paired with an configuration-specific private salt, in addition to using multiple hash iterations. <p/> While one can do this easily enough using Shiro's {@link Hash} implementations directly, this direct approach could quickly lead to copy-and-paste behavior. For example, consider this logic which might need to repeated in an application: <pre> int numHashIterations = ... ByteSource privateSalt = ... ByteSource randomSalt = {@link hunt.shiro.crypto.RandomNumberGenerator randomNumberGenerator}.nextBytes(); ByteSource combined = combine(privateSalt, randomSalt); Hash hash = Sha512Hash(source, combined, numHashIterations); save(hash); </pre> In this example, often only the input source will change during runtime, while the hashing strategy (how salts are generated or acquired, how many hash iterations will be performed, etc) usually remain consistent. A HashService internalizes this logic so the above becomes simply this: <pre> HashRequest request = new HashRequest.Builder().source(source).build(); Hash result = hashService.hash(request); save(result); </pre>